Collagen is the collective term for a group of insoluble fibrous proteins. It is the chief constituent of the fibrils of connective tissue, hide, and tendons. Historically, it has been a source of primitive glue and gelatin extracted from animal parts by prolonged boiling.
Collagen is also a natural polymer. Injectable collagens are various types of liquid emulsion in which collagen is emulsified in a pharmaceutical carrier, such as a saline solution, which can be injected into a patient for soft tissue augmentation. Since it is a bio-material that is usually accepted by the patient's immune system with little or mild host reaction, it is generally preferred over inorganic augmentation material, such as injectable silicone (polydimethylsiloxane).
Commercially available injectable collagen which has been approved for medical use has been predominantly produced from bovine tissue. An example is Zyderm Collagen Implant (ZCI) and Zyplast Collagen Implant (ZI) produced by Collagen Corporation of Palo Alto, California, using collagen extracted from cow skin as the base material.
Despite its superiority to injectable silicone, bovine and other animal-source collagen is still identified as a foreign substance by the human host immune system. Although the immunological reaction is mild in most subjects, producing only short-duration symptoms of local inflammation, a significant percentage of the population will exhibit a more severe reaction. This risk mandates a skin patch test prior to approval for treatment with injectable collagen. The test typically comprises injecting a small quantity of the particular bovine collagen product under the skin of the forearm, and assessing the inflammation response over a period of approximately four weeks. Further, subjects having a history of autoimmune disease are precluded from receiving injectable collagen treatment.
In addition to the risk of allergic reaction, bovine collagen does not exhibit long-term residence at the injection site, and thus requires periodic touch-up injections. It is believed that the reason for dispersion of the bovine collagen is that the fibroblast cells are destroyed when the collagen is extracted from the hides by pepsin digestion and filtration. The absence of linking tissue allows the collagen to be absorbed by the host and not replaced in equal volume at the site by the subject's natural collagen.
Human collagen has heretofore been rarely used except in laboratory testing and experimental procedures, and has typically come from cadavers.
The present inventor and his colleagues proposed at the Sixth Annual Scientific Meeting of the American Academy of Cosmetic Surgery on Jan. 12-14, 1990, that collagen could be derived from a patient's own adipose tissue extracted by liposuction procedures, and processed into an injectable form for immediate use or stored for future use. The reticular fiber connecting adipose tissue is known to be constituted mainly of collagen. Such material, being of patient's own tissue and retaining its fibrous composition, would not trigger an immunological reaction nor dispersion from the injection site. The inventor has now developed a method and apparatus for accomplishing this objective.